Wijk et al. (1967, 1969) listed 87 species of Ptychomitrium in the world. Crosby et al. (2000) reduced this number to 54 species, 34 of which were given their highest confidence rating (four stars). T. Cao, C. Gao and Vitt (1995) recognized eight species in China. A new species, Ptychomitrium mamillose was recently published by S.-L. Guo et al. (2000) from Sichuan province.

The distinguishing features of Ptychomitrium can be generalized as follows: 1) leaves often crisped or strongly incurved or contorted when dry; 2) calyptrae large, mitrate, covering a large portion of capsules, longitudinally plicate and lobed at the base; 3) peristome teeth haplolepideous, lanceolate to linear-lanceolate, irregularly splitting into 2–3 filiform, densely papillose segments; 4) costa single, strong, percurrent to subpercurrent; 5) the upper leaf cells rounded-quadrate to subquadrate, more or less thick-walled, smooth; and 6) the basal leaf cells elongate, thin-walled or with sinuose walls.